Method of refining liquid fats and oils



United States Patent 6 Claims. (of. 260-424) This invention relates tothe refining of vegetable and animal oils and fats in the liquid state,and more particularly to the refining of edible fats and oils.

Crude oils and liquid fats of vegetable or animal origin, referred tojointly hereinafter as oil, usually require refining for removal of suchundesired components as suspended solid particles, colorants, and freefatty acid. It is conventional to admix alkaline compounds which combinewith the free fatty acids to form soaps. The mixture is treated withsolid, particulate adsorbents such as fullers earth or activatedcharcoal, filtered, and may then be subjected to steam distillation in afairly high vacuum to remove most of the odoriferous constituents.

The afore-described conventional process inevitably causes somesaponification of the desired glycerides together with the fatty acids.The glyceride losses are sutficiently high to affect the economics ofthe process.

It was therefore proposed heretofore to employ acids, acid salts, orstrongly dissociated neutral salts in aqueous solution for refiningcrude oils. A saponification of glycerides is readily avoided with suchrefining agents. It has been found difiicult, however, to obtainadequate removal of contaminants when the time of contact between theliquid product and the refining acid or salt solution is reasonablyshort. Mechanical agitation is not effective in accelerating thereaction to the necessary extent. Unless a very large excess of refiningagent is used in conjunction with intensive mechanical mixing, theresults obtained within practical processing periods are disappointing.

I have found that relatively small amounts of acids, acid salts, orstrong electrolytes whose pH is not much above 7 may be employed over ashort period of contact in the refining of oils if the refining agent isdispersed colloidally in the glyceride material to form an emulsion thedispersed phase of which includes the refining agent. The emulsion maybe produced and maintained by means of any suitable surface activeagent.

The refining agents which have been employed successfully in my methodinclude the mineral acids, including sulfuric acid and solutions ofsulphur dioxide (sulfurous acid), phosphoric acid, hydrochloric acid,and their salts such as sodium bisulfate, sodium sulfite, potassiumsulfate, sodium chloride, sodium hydrogen phosphates, organic acids suchas formic acid, acetic acid, oxalic acid, citric acid, and also theiranhydrides, for example, acetic anhydride.

Suitable surface active emulsifying agents include the commerciallyavailable monoand diglycerides of naturally occurring saturated andunsaturated fatty acids, sulfates and sulfonates of fatty alcohols,non-ionic surfactants such as those derived from ethylene oxide, andcationic surface active compounds such as the well known long chainamine salts.

In carrying out the method of my invention, I first combine the refiningagent with the emulsifying agent and with Water, if water is employed asa diluent or solvent. The sequence of mixing the refining agent, theemulsifying agent, and the water, if any, will readily suggest itslf tothose skilled in the art. The mixture is then stirred with the oil thatit is desired to refine. It is also possible first to disperse theemulsifying agent in the oil and then to admix the refining agenttogether with any water used,

3,354,188 Patented N av. 21, 1967 whereby a water-in-oil type emulsionis formed in which the oil phase is continuous, whereas the dispersedphase contains the water and refining agent which are practical lyinsoluble in the oil.

If the amount of suspended refining agent is small, fullers earth,activated clay, charcoal, or a similar solid adsorbent having a higheffective surface-to-weight ratio may be admixed to the oil while itcontains the refining agent so that the suspended phase is retained onthe solid adsorbent together with certain impurities.

If removal of coloring constituents is not necessary, or if it is to becarried out separately, filter aids such as diatomaceous earth(kieselguhr) or asbestos fibers are admixed to the oil, and the mixtureis filtered. The aforementioned adsorbent is similarly removed byfiltration. In either case, the excess of refining agent, any waterpresent and not dissolved in the oil phase, and virtually all of theemulsifying agent is removed from the oil by the filtration step.

If filtering is not practical, decantation, centrifugal separation, andsimilar processes may be resorted to in a known manner.

The method of the invention has been employed successfully with soybeanoil, rapeseed oil, sesame oil, castor oil, coconut oil, palm oil,linseed oil, fish oils, whale oil, and mustard oil.

Separation of the refining agent from the oil may be followed by steamdistillation in a vacuum in a manner conventional in itself. The fattyacids removed there-by are of high purity, show good color, and are freefrom contaminants. The steam distillation process is readily conductedin such a manner as to hold the amount of neutral oil in the fatty acidsto a minimum.

The following example is further illustrative of the instant invention,but it will be understood that the invention is not limited thereto.

Example Five parts 70% phosphoric acid and five parts glycerolmonostearate as an emulsifiying agent were intimately mixed with eachother. The resulting emulsion readily dispersed in 1000 parts crudecoconut oil containing 4.6% free fatty acids and having a temperature of30 C. A uniform emulsion of the water-in-oil type was formed thereby.Fifteen parts fullers earth were then admixed, and the temperature wasraised to 94 C. over a period of several hours while stirring continued.The hot mixture was filtered.

The filtrate was clear. It was subjected to steam distillation for fourhours at 237 C. at a pressure of 4 mm. Hg. Fatty acids and odor-causingvolatile constituents were thereby removed. The residue contained 0.06%free fatty acid. It included 97.3% of the neutral oil originallypresent. The product met all requirements for refined coconut oil ofhigh quality.

The distillate was light in color, and free from objectionablecontaminants. It consisted essentially of free fatty acid containing 19%neutral coconut oil. The small amount of neutral oil not accounted forin the distillate and in the distillation residue was found adsorbed onthe fullers earth. It was recovered therefrom by solvent extraction.

The dispersion of chemical bleaching agents together with the refiningagents of the invention is advantageous where the nature of the refiningagent and the bleaching agent permits, and will be obvious to thoseskilled in the art.

While the invention has been described with particular reference tospecific embodiments, it is to be understood that it is not limitedthereto, but is to be construed broadly and restricted solely by thescope of the appended claims.

What is claimed is:

1. A method of refining a liquid oil which comprises emulsifying in saidoil an effective amount of a refining agent in the presence of anemulsifying agent, said refining agent being substantially insoluble insaid oil, and being a liquid having a pH not substantially higher than 7adsorbing the emulsified refining agent on a particulate solid; andseparating said solid having said refining agent adsorbed thereon fromsaid oil.

2. A method as set forth in claim 1, wherein said refining agent is anaqueous solution of an acid.

3. A method as set forth in claim 2, wherein said emulsifying agent isglycerol monostearate, and said acid is phosphoric acid.

4. A method of refining a crude edible oil which comprises:

(a) dispersing in said oil in the liquid state an effective amount of arefining agent selected from the group consisting of sulfuric acid,sulfurous acid, phosphoric acid, hydrochloric acid, formic acid, aceticacid, oxalic acid, citric acid, alkali metal salts of said acids havinga pH not substantially greater than 7, and acetic anhydride, or anaqueous solution of said refining agent in the presence of a sufficientamount of an emulsifying agent to form an emulsion, the agent or theaqueous solution thereof constituting the'dispersed phase of saidemulsion and said oil constituting the continuous phase of the emulsion;

(b) adsorbing said dispersed phase on a particulate solid; and

(c) separating said solid having said dispersed phase adsorbed thereonfrom said continuous phase.

5. A method as set forth in claim 4, wherein said oil is soybean oil,rapeseed oil, sesame oil, castor oil, coconut oil, palm oil, linseedoil, fish oil, whale oil, or mustard oil.

6. A method as set forth in claim 4, wherein the separated continuousphase is subjected to steam distillation.

References Cited UNITED STATES PATENTS 2,525,702 10/ 1950 Mattikow260420 2,694,082 11/ 1954 Palmqvist 260-424 HENRY R. JILES, ActingPrimary Examiner. R. BOYD, A. M. TIGHE, Assistant Examiners.

4. A METHOD OF REFINING A CRUDE EDIBLE OIL WHICH COMPRISES: (A)DISPERSING IN SAID OIL IN THE LIQUID STATE AN EFFECTIVE AMOUNT OF AREFINING AGENT SELECTED FROM THE GROUP CONSISTING OF SULFURIC ACID,SULFUROUS ACID, PHOSPHORIC ACID, HYDROCHLORIC ACID, FORMIC ACID, ACETICACID, OXALIC ACID, CITRIC ACID, ALKALI METAL SALTS OF SAID ACIDS HAVINGA PH NOT SUBSTANTIALLY GREATER THAN 7, AND ACETIC ANHYDRIDE, OR ANAQUEOUS SOLUTION OF SAID REFINING AGENT IN THE PRESENCE OF A SUFFICIENTAMOUNT OF AN EMULSIFYING AGENT TO FORM AN EMULSION, THE AGENT OR THEAQUEOUS SOLUTION THEREOF CONSTITUTING THE DISPERSED PHASE OF SAIDEMULSION AND SAID OIL CONSTITUTING THE CONTINUOUS PHASE OF THE EMULSION;(B) ADSORBING SAID DISPERSED PHASE ON A PARTICULATE SOLID; AND (C)SEPARATING SAID SOLID HAVING SAID DISPERSED PHASE ADSORBED THEREON FROMSAID CONTINUOUS PHASE.